1. Field of the Invention
The invention relates in general to an optical system, and more particularly to an optical system with reflection type diffraction grating.
2. Description of the Related Art
There are many different ways to decompose or separate the composition of a substance to understand its ingredients such as the composition of or the compounds in water. The process of decomposition and separation employed in above test are all destructive, and normally necessary testing processes are conducted in response to the needs. In contrast, the spectrum analyzer is a non-destructive testing instrument, which recognizes the ingredients and the properties of a substance according to atomic or molecular energy levels and chemical bonds of the substance. According to the reflection theory of the light, the compositional structures of substances are different from each other in terms of reflection, absorption and penetration for the light with different frequency bands, and different substances have their respective spectrum arranged according to the wavelength.
Referring to FIG. 1, a conventional spectrum analyzer is shown. After the light 900 generated by the light source 810 is emitted to the spectrum analyzer 800 via the slit 820, the light 900 is emitted to a collimating mirror 830 in free space and is converted to a parallel light which is then emitted to a plane grating 840. The light being divided by the diffraction structure 842 of the grating 840 is then focused by the focusing mirror 850 and emitted to the optical detector 860 to detect the intensity of the light with different wavelengths to generate a corresponding image. However, the conventional spectrum analyzer uses a plane grating, which requires the use of a collimating mirror and a focusing mirror for accurately dividing and focusing the light. Since the process of precisely aligning the optical components is very complicated and the number of components is large, minor vibrations may cause the alignment of the optical components to shift and incur more manufacturing and maintenance costs, not only creating inconvenience of use but also jeopardizing the object of miniaturizing the spectrum analyzer and achieving portability.